1. Field of the Invention
An aspect of the present invention relates to a digital broadcasting transmission system and a method thereof. More particularly, an aspect of the present invention relates to a digital broadcasting transmission system enabling an improved receptivity, by using a variety of methods to code a turbo stream, and a method thereof.
2. Description of the Related Art
According to the Advanced Television System Committee (ATSC) Digital Vestigial Side Band (VSB) technologies, the U.S. oriented terrestrial digital broadcasting system uses a single carrier and field sync signal of 312-segment unit. This system has poor receptivity particularly in the bad channel such as Doppler fading channel.
FIG. 1 is a block diagram of a conventional ATSC VSB broadcasting transmission apparatus, and FIG. 2 shows the frame structure of data used in the system of FIG. 1.
More specifically, FIG. 1 shows an EVSB system, which makes and sends out a dual transport stream (TS) by adding robust data to the normal data of an existing ATSC VSB system.
Referring to FIG. 1, the transmission of the conventional digital broadcasting transmission system is explained below.
A normal stream, a place holder packet and a turbo stream are fed to a TS constructor 11 in which a dual TS is constructed.
The dual TS is randomized at the randomizer 13, a parity bit is appended to the transmitted stream for error correction at a Reed-Solomon (RS) encoder 15, and a packet is re-constructed at a packet formatter 17. Additionally, the re-constructed packet is interleaved at an interleaver 19, and the interleaved data is trellis-encoded at a trellis encoder 21. The trellis encoder 21 generates a compatible parity bit through an interaction with a compatible parity generator 23.
After the data is error-corrected at the trellis encoder 21, the error-corrected data is multiplexed at a multiplexer (MUX) 27 which inserts field sync and segment sync signals in the data. Then the processes of pilot signal insertion, VSB conversion and up-conversion to RF channel signal levels, are performed and the data is transmitted through the channel. The above operations may be controlled by the control signal from a controller 25.
As shown in FIG. 2, a data frame that is applied to the digital broadcasting transmission apparatus of FIG. 1 has consecutive packets M0 through M51, and is formatted at a packet formatter 17 and outputted. As shown, the turbo stream and the normal stream are arranged at the rate of 1:3.
A problem of the VSB system is performance degradation due to dynamic multipath interference and a weak signal. However, notwithstanding the fact that they use a dual TS which includes normal stream added with turbo stream, the conventional digital broadcasting transmission systems, as the ones shown in FIGS. 1 and 2, could hardly improve bad receptivity by the transmission of a normal stream in the multipath channel.
Additionally, at relatively high power levels, that is, as 4th level power used among the existing 8 levels of power, average power consumption of the stream increases. If many turbo streams are used, quality of normal stream will relatively deteriorate. Therefore, adding a turbo stream to the normal stream has to be limited.